Cut the tuna into long, fat, squared-off strips or "logs" 1 to 1-1/2 inches thick. Coat the tuna with the oil and season lightly with salt and pepper. Set a 10-inch heavy-duty skillet over high heat. When the pan is very hot, after 2 to 3 minutes, sear the tuna logs for 20 to 30 seconds on each s...